Compression ignition engines provide advantages in fuel economy, but produce both NOx and particulates during normal operation. New and existing regulations continually challenge manufacturers to achieve good fuel economy and reduce the particulates and NOx emissions. Lean-burn engines achieve the fuel economy objective, but the high concentrations of oxygen in the exhaust of these engines yields significantly high concentrations of NOx as well. Accordingly, the use of NO reducing exhaust treatment schemes are being employed in a growing number of systems.
One such system is the direct addition of ammonia gas to the exhaust stream. It is an advantage to deliver ammonia directly in the form of a gas, both for simplicity of the flow control system and for efficient mixing of reducing agent, ammonia, with the exhaust gas. The direct use of ammonia also eliminates potential difficulties related to blocking of the dosing system, which are cause by precipitation or impurities, e.g., in a liquid-based urea solution. In addition, an aqueous urea solution cannot be dosed at a low engine load since the temperature of the exhaust line would be too low for complete conversion of urea to ammonia (and CO2).
Transporting ammonia as a pressurized liquid, however, can be hazardous if the container bursts caused by an accident or if a valve or tube breaks. In the case of using a solid storage medium, the safety issues are much less critical since a small amount of heat is required to release the ammonia and the equilibrium pressure at room temperature can be—if a proper solid material is chosen—well below 1 bar. Ammonia can be provided in the form of disks or balls loaded into the canister. Typically, once the ammonia is used up, the canister and its contents are destroyed and recycled. Attempts have been made to recharge the ammonia; however, introduction of gaseous ammonia into a compressed material in previous techniques, typically results in very slow absorption and saturation, often taking several hours.
The present device and method of recharging or adsorbing an ammonia-containing material contained within a cartridge or canister resulting in equal distribution of the ammonia throughout the material in the cartridge. The present device and method results in a quicker, more efficient saturation and recharging of material than previous devices and methods. In this manner, cartridges and their contents can be re-used, perhaps even multiple times, resulting in cost savings for manufacture and recycling.